Far-field and near-field ultrasound imaging device

ABSTRACT

Devices, systems, and methods for ultrasonically acquiring far-field and near-field images within a body are disclosed. An ultrasound imaging device adapted for insertion within a body includes a first ultrasonic sensor configured to transmit ultrasonic waves at a first frequency for acquiring far-field images within the body, and a second ultrasonic sensor configured to transmit ultrasonic waves at a higher frequency than the first frequency for acquiring near-field images within the body. The ultrasound imaging device can be connected to a control device and user interface for visualizing far-field and near-field images acquired by the ultrasonic sensors.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Application No. 13/400,253,filed Feb. 20, 2012, which claims priority to Provisional ApplicationNo. 61/466,107, filed Mar. 22, 2011, and entitled “Far-Field andNear-Field Ultrasound Imaging Device,” the contents of which areincorporated herein by reference in their entirety for all purposes.

TECHNICAL FIELD

The present disclosure relates generally to imaging devices and systemsfor imaging medical probes and anatomical structures within the body.More specifically, the present disclosure relates to ultrasound imagingdevices and systems capable of visualizing medical probes, anatomicalstructures, and body tissue in both the far-field and near-field.

BACKGROUND

In many diagnosis and interventional procedures, it is often necessaryto determine the location of a medical probe or catheter relative to alocation of interest within the body. In interventional cardiacelectrophysiology procedures, for example, it is often necessary for thephysician to determine in real-time the location of a medical probe suchas a electrophysiology mapping catheter or therapeutic deliveringcatheter (e.g., an ablation catheter) relative to the patient's internalanatomy. During such procedures, the physician may deliver the mappingcatheter through a main vein or artery into an interior region of theheart to be treated. Using the mapping catheter, the physician may thendetermine the source of the cardiac rhythm disturbance or abnormality byplacing a number of mapping elements carried by the catheter intocontact with the adjacent cardiac tissue and then operating the catheterto generate an electrophysiology map of the interior region of theheart. Once a map of the heart is generated, the physician may thenadvance an ablation catheter into the heart, and position an ablatingelement carried by the catheter tip near the targeted cardiac tissue toablate the tissue and form a lesion, thereby treating the cardiac rhythmdisturbance or abnormality.

The navigation of medical probes such as mapping and ablation cathetershas traditionally been accomplished using fluoroscopic techniques inwhich radiopaque elements located at or near the distal end of the probeare used to fluoroscopically image the probe as it is routed through thebody. Such systems produce a two-dimensional image of the probe, asrepresented by the illuminated radiopaque element, allowing thephysician to ascertain the general location of the probe. Althoughfluoroscopy is commonly used in EP procedures, such technique does notpermit the imaging of soft tissues, making it difficult for thephysician to visualize features of the anatomy as a reference fornavigation.

Various ultrasound-based imaging catheters and probes have beendeveloped for directly visualizing medical probes in applications suchas interventional cardiology, interventional radiology, andelectrophysiology. For interventional cardiac electrophysiologyprocedures, for example, ultrasound imaging devices have been developedthat permit the visualization of anatomical structures of the heartdirectly and in real-time. In some electrophysiology procedures, forexample, ultrasound catheters may be used to image the intra-atrialseptum, to guide transseptal crossing of the atrial septum, to locateand image the pulmonary veins, and to monitor the atrial chambers of theheart for signs of a perforation and pericardial effusion. Manyultrasound-based imaging devices are designed to image in the far-fieldat a distance greater than about 1 cm, allowing the physician tovisualize anatomical structures, the position of devices relative tothose structures, as well as any anomalies or interestingcharacteristics of those structures. These devices typically operate atlower ultrasonic frequencies of between about 2 to 15 MHZ in order tobalance far-field tissue/blood penetration against far-field resolutionand image quality.

In some procedures, it may be desirable to visualize tissue that is inclose proximity to the imaging device (e.g., at or less than about 1 cm)in order to determine the characteristics of that tissue. For example,such feedback may help the physician to determine whether the device isin contact with tissue, to determine whether the tissue is healthytissue or scar tissue, to determine the thickness of the tissue, todetermine whether an ablation lesion is transmural or continuous withadjacent lesions, as well as other characteristics.

SUMMARY

The present disclosure relates to ultrasound imaging devices and systemscapable of visualizing medical probes, anatomical structures, and bodytissue in both the far-field and near-field.

In Example 1, an ultrasound imaging device adapted for insertion withina body comprises an elongate housing having a proximal section and adistal section; a first ultrasonic sensor configured to operate inalternating pulsing and sensing modes, the first ultrasonic sensordisposed within the distal section and configured to transmitsubstantially side-directed ultrasonic waves at a first frequency foracquiring far-field images within the body; a second ultrasonic sensordisposed within a distal tip and configured to operate in alternatingpulsing and sensing modes, the second ultrasonic sensor configured totransmit substantially forward-directed ultrasonic waves at a secondfrequency greater than the first frequency for acquiring near-fieldimages within the body; and a means for rotating at least one of thefirst and second ultrasonic sensors within the housing.

In Example 2, the ultrasound imaging device of Example 1, wherein themeans for rotating at least one of the first and second ultrasonicsensors includes a rotating element coupled to both the first and secondultrasonic sensors.

In Example 3, the ultrasound imaging device of Example 1, wherein themeans for rotating at least one of the first and second ultrasonicsensors includes a first actuator coupled to the first ultrasonic sensorand a second actuator coupled to the second ultrasonic sensor.

In Example 4, the ultrasound imaging device of Example 1, wherein themeans for rotating at least one of the first and second ultrasonicsensors includes a rotating driveshaft coupled to the first ultrasonicsensor and a motor coupled to the second ultrasonic sensor.

In Example 5, the ultrasound imaging device of any of Examples 1-4,wherein the first ultrasonic sensor is configured to direct ultrasonicwaves at a transmission angle of between about 10 to 40 degrees.

In Example 6, the ultrasound imaging device of any of Examples 1-5,wherein the second ultrasound sensor is configured to direct ultrasonicwaves at transmission angle of between about 10 to 40 degrees.

In Example 7, the ultrasound imaging device of any of Examples 1-6,further comprising a means for dynamically adjusting the direction ofthe ultrasonic waves transmitted by at least one of the first and secondultrasonic sensors.

In Example 8, the ultrasound imaging device of any of Examples 1-7,wherein the second ultrasonic sensor comprises a plurality of ultrasonictransducer elements, and wherein the means for dynamically adjusting thedirection of at least one of the first and second ultrasonic wavesincludes a means for adjusting phase delays on one or more of thetransducer elements.

In Example 9, the ultrasound imaging device of any of Examples 1-8,further comprising a steering wire configured for steering the distalsection of the housing.

In Example 10, the ultrasound imaging device of any of Examples 1-9,further comprising at least one electrode configured for sensingelectrical activity within the body.

In Example 11, an ultrasound imaging device adapted for insertion withina body comprises an elongate housing having a proximal section, a distalsection, and a distal tip; a first ultrasonic sensor configured foracquiring far-field images within the body, the first ultrasonic sensordisposed within the distal section of the housing and configured totransmit substantially side-directed ultrasonic waves at a firstfrequency; and a second ultrasonic sensor configured for acquiringnear-field images within the body, the second ultrasonic sensor disposedwithin the distal tip and configured to transmit substantiallyforward-directed ultrasonic waves at a second frequency greater than thefirst frequency.

In Example 12, an apparatus for acquiring far-field and near-fieldultrasonic images within a body comprises a control device; anultrasound imaging device coupled to the control device, the ultrasoundimaging device including a housing having a proximal section and adistal section, a first ultrasonic sensor configured to transmitsubstantially side-directed ultrasonic waves at a first frequency foracquiring far-field images within the body, and a second ultrasonicsensor configured to transmit substantially forward-directed ultrasonicwaves at a second frequency greater than the first frequency foracquiring near-field images within the body; and a user interfaceconfigured for visualizing far-field and near-field images acquired bythe first and second ultrasonic sensors.

In Example 13, the apparatus of Example 12, wherein the ultrasoundimaging device further includes a means for rotating at least one of thefirst and second ultrasonic sensors.

In Example 14, the apparatus of any of Examples 12-13, wherein the firstultrasonic sensor is disposed within the housing proximal to the secondultrasonic sensor, and is configured to transmit substantiallyside-directed ultrasonic waves from a side of the housing.

In Example 15, the apparatus of any of Examples 12-14, wherein thesecond ultrasonic sensor is disposed within a distal tip of the housing,and is configured to transmit substantially forward-directed ultrasonicwaves from the housing.

In Example 16, the apparatus of any of Examples 12-15, wherein thecontrol device includes a controller, a rotary joint, a motor encoder,and an image processor.

In Example 17, the apparatus of any of Examples 12-16, wherein thecontrol system is configured to rotate at least one of the first andsecond ultrasound sensors within the housing.

In Example 18, the apparatus of any of Examples 12-17, furthercomprising a means for rotating the first and second ultrasonic sensorswithin the housing, and wherein the control device is configured forcontrolling the rotation of one or both of the first and second sensors.

In Example 19, the apparatus of any of Examples 12-18, furthercomprising a means for dynamically adjusting the direction of ultrasonicwaves transmitted by at least one of the first and second ultrasonicsensors.

In Example 20, the apparatus of any of Examples 12-19, wherein at leastone of the first and second ultrasonic sensors includes a plurality oftransducer elements, and wherein the control device is configured todynamically adjust the direction of ultrasonic waves transmitted by thetransducer elements.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram showing a medical system inaccordance with an illustrative embodiment;

FIG. 2 is a schematic view showing an ultrasound imaging device inaccordance with an illustrative embodiment;

FIG. 3 is a schematic view showing the distal section of the ultrasoundimaging device of FIG. 2 in greater detail;

FIG. 4 is a schematic view showing the distal section of an ultrasoundimaging device in accordance with another illustrative embodiment;

FIG. 5 is a schematic view showing the distal section of an ultrasoundimaging device in accordance with another illustrative embodiment;

FIG. 6 is a schematic view showing the distal section of an ultrasoundimaging device in accordance with another illustrative embodiment;

FIG. 7 is a flow diagram showing an illustrative process for visualizinganatomical structures, body tissue, and other medical devices within thebody using the ultrasound imaging device of FIG. 2;

FIG. 8 is a view showing an ultrasound imaging device implanted in theright atrium of the heart and configured for visualizing a medical proberelative to cardiac anatomy; and

FIG. 9 is an enlarged view showing the transmission of ultrasonic wavesfrom the ultrasound imaging device of FIG. 8.

While the invention is amenable to various modifications and alternativeforms, specific embodiments have been shown by way of example in thedrawings and are described in detail below. The intention, however, isnot to limit the invention to the particular embodiments described. Onthe contrary, the invention is intended to cover all modifications,equivalents, and alternatives falling within the scope of the inventionas defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 is a functional block diagram showing a medical system inaccordance with an illustrative embodiment. The system 10,illustratively a system for mapping and treating a heart 12, includes amapping/ablation subsystem 14 for mapping and ablating tissue within theheart 12, an imaging subsystem 16 for generating high resolution imagesof anatomical structures and body tissue in or near the heart 12, and auser interface 18 for registering mapping data and visualizinganatomical structures and body tissue as well as the movement of othermedical devices in or near the heart 12.

The mapping/ablation subsystem 14 may be used for identifying andtreating a target tissue site or multiple sites within the body such asan aberrant conductive pathway. In the embodiment of FIG. 1, themapping/ablation subsystem 14 comprises a mapping/ablation catheter 20including one or more sense/treatment electrodes 22, a mapping processor24, and a radio frequency (RF) generator 26. An example mapping/ablationcatheter 20 that can be operated to detect electrical signals inmyocardial tissue for use in identifying target treatment sites and/orfor providing ablation energy to target sites is further described, forexample, in U.S. Pat. No. 7,720,520, which is expressly incorporatedherein by reference in its entirety for all purposes. Other types ofmapping/ablation catheters 20 can also be used. In some embodiments, forexample, the catheter can comprise a basket-type structure of resilientsplines each including one or more sense/ablation electrodes. In yetother embodiments, the catheter can include one or more rovingsense/ablation electrodes that can be steered into contact withidentified ablation sites. In some embodiments, an ablation catheterwith a dedicated ablation electrode or electrodes can be used inconjunction with a separate mapping catheter.

The mapping processor 24 is configured to derive activation times andvoltage distribution from the electrical signals obtained from theelectrodes 22 to determine irregular electrical signals within the heart12, which can then be graphically displayed as a map on the userinterface 18. Further details regarding electrophysiology mapping areprovided, for example, in U.S. Pat. Nos. 5,485,849, 5,494,042,5,833,621, and 6,101,409, each of which are expressly incorporatedherein by reference in their entirety for all purposes.

The RF generator 26 is configured to deliver ablation energy to anablation electrode (e.g., a distal-most electrode 22 of themapping/ablation catheter 20) in a controlled manner to ablate any sitesidentified by the mapping processor 24. Other types of ablation sourcesin addition to or in lieu of the RF generator 26 can also be used forablating target sites. Examples of other types of ablation sources caninclude, but are not limited to, microwave generators, acousticgenerators, cryoablation generators, and laser/optical generators.Further details regarding RF generators are provided, for example, inU.S. Pat. No. 5,383,874, which is expressly incorporated herein byreference in its entirety for all purposes.

In the embodiment of FIG. 1, the imaging subsystem 16 includes a driveand control system 28 that can be used for controlling an ultrasoundimaging device 30 adapted to visualize anatomical structures, bodytissue, as well as the other implanted medical devices located relativeto those structures and tissue. In certain embodiments, the drive andcontrol system 28 includes a controller 32, a rotary joint 34, and amotor encoder 36. In some embodiments, the controller 32 and rotaryjoint 34 are configured to control the rotation of a driveshaft 76 (seeFIG. 3) that extends through an interior lumen of the ultrasound imagingdevice 30 to a distal section of the device 30. During this rotation,the motor encoder 36 is configured to detect the instantaneousrotational position of the driveshaft via the rotary joint 34, andprovides a feedback signal containing the current driveshaft positionback to the controller 32, which can then be used to generate scanimages from a far-field ultrasonic sensor 38 and near-field ultrasonicsensor 40, as discussed further below. Connection of the rotary joint 34and motor encoder 36 to the ultrasound imaging device 30 can beaccomplished, for example, via a motor/drive shaft connector 58described further herein with respect to FIG. 2.

During operation, the controller 32 is configured to monitor and controlthe positioning of the far-field ultrasonic sensor 38 and near-fieldultrasonic sensor 40 carried by the ultrasound imaging device 30. Incertain procedures, for example, the controller 32 can be configured tomonitor and control the position of the ultrasound imaging device 30within a right atrium in order to visualize the anatomy and the presenceof a mapping/ablation catheter 20 within the atrium using the far-fieldultrasonic sensor 38 as well as the status of soft body tissue withinthe atrium using the near-field ultrasonic sensor 40. As used herein,the terms “far-field” and “near-field” are relative terms that describethe ability of the ultrasonic sensors 38,40 to accurately reproduceimages of anatomy and/or objects located a certain distance away fromthe sensor. The distance at which the sensors 38,40 can visualizeanatomy and objects within the body is dependent on the mechanicalcharacteristics of the sensors 38,40, the electrical characteristics ofthe sensor circuitry including the drive frequency that drives thesensors 38,40, the attenuation and boundary conditions between thesensors 38,40 and the surrounding anatomy, as well as other factors.

In some cardiac procedures such as interventional cardiacelectrophysiology, the relative term “far-field” can be definedgenerally as a distance greater than about 1 cm away from the sensorsurface whereas the relative term “near-field” can be defined generallyas a distance at or less than 1 cm away from the sensor surface. Thedistances that define whether the sensor 38,40 generates images in the“far-field” or “near-field” can vary, however, depending on theparticular procedure to be performed. In applications for detecting andtreating neurological disorders, for example, the ultrasonic sensors38,40 can each be configured to visualize objects at different relativedistances than in cardiac applications due to the differing anatomy ofthe brain and brain tissue.

The electrical signals sensed by each of the ultrasonic sensors 38,40can be fed to an imaging processor 42, which combines the signals withthe positioning information from the controller 32 to produce both afar-field image and a near-field image on a display monitor 44 of theuser interface 18. In some embodiments, an image merger 46 is configuredto superimpose graphical information from the medical image dataacquired from the imaging subsystem 16 and superimpose that informationon the display monitor 44 along with graphical information acquired fromother sources (e.g., a fluoroscopic monitor) and/or position informationfrom the mapping/ablation subsystem 14 to form a composite medicalimage.

Although the system 10 is described in the context of a mapping andablation system for use in intracardiac electrophysiology procedures fordiagnosing and treating the heart, in other embodiments the system 10may be used for treating, diagnosing, or otherwise visualizing otheranatomical bodies such as the prostate, brain, gall bladder, uterus,esophagus, and/or other regions in the body. Moreover, many of theelements in FIG. 1 are functional in nature, and are not meant to limitthe structure that performs these functions in any manner. For example,several of the functional blocks can be embodied in a single device, orone or more of the functional blocks can be embodied in multipledevices.

FIG. 2 is a schematic view showing an ultrasound imaging device 30 inaccordance with an illustrative embodiment for use with the system 10 ofFIG. 1. As shown in FIG. 2, the ultrasound imaging device 30 includes anelongate tubular housing 48 having a proximal section 50 and a distalsection 52. The proximal section 50 of the housing 48 is coupled to aproximal hub 54, which includes a fluid port 56 for providing acousticcoupling/cooling fluid to one or both of the ultrasonic sensors 38,40.The proximal hub 54 is connected to the drive and control system 28 viaa connector 58, which supports the hub 54 in a stationary position asthe rotary joint 34 applies rotary motion 60 to rotate each of theultrasonic sensors 38,40 within the housing 48.

In some embodiments, the ultrasonic sensors 38,40 each comprisepiezoelectric transducers formed of a polymer such as PVDF or apiezoceramic material such as PZT. A number of leads (not shown) thatextend through the interior space of the housing 48 connect theultrasonic sensors 38,40 to the drive and control system 28. Duringultrasonic imagining, each of the ultrasonic sensors 38,40 areconfigured to operate in alternating pulsing and sensing modes. Whenexcited electrically in the pulsing mode, the ultrasonic sensor 38,40creates pressure waves 62,66 which travel through the housing 48 andinto the surrounding environment. In the sensing mode, the ultrasonicsensors 38,40 each produce an electrical signal as a result of receivingacoustic waves reflected back to the sensors 38,40, which are thenprocessed and displayed on the display monitor 44 of the user interface18. These reflections are generated by the acoustic waves 62,66traveling through changes in density in the surrounding environmentbeing imaged.

In the embodiment of FIG. 2, the far-field ultrasonic sensor 38 islocated at a position along the housing 48 proximal to the near-fieldultrasonic sensor 40, and is configured to transmit and receive acousticwaves 62 from the side of the housing 48 for visualizing anatomicalstructures and/or other medical devices in the far-field. In certainembodiments, for example, the far-field ultrasonic sensor 38 isconfigured to deliver acoustic waves 62 at a frequency of between about2 to 15 MHz and in a side-oriented direction that is substantiallyperpendicular to a length of the housing 48. The near-field ultrasonicsensor 40, in turn, is located at or near the distal tip 64 of thehousing 48, and is configured to transmit and receive acoustic waves 66in a substantially forward-oriented direction for visualizing bodytissue and other structures in the near-field. In certain embodiments,for example, the near-field ultrasonic sensor 40 is configured todeliver acoustic waves 66 at a frequency greater than about 20 MHz andin a forward-oriented direction from the distal tip 64 of the housing48.

The ultrasound imaging device 30 further includes a radiopaque marker 68that can be used to fluoroscopically monitor the location of the device30 within the body. In some embodiments, the device 30 also includes oneor more electrodes 70,72 on its outer surface to permit the recording ofelectrical signals, and in some cases, the delivery of electricalsignals. In certain embodiments, the electrodes 70,72 can also be usedto facilitate position tracking of the device 30 using a positiontracking system. Although the device 30 shown in FIG. 2 includes asingle far-field ultrasonic sensor 38 and a single near-field ultrasonicsensor 40, in other embodiments multi far-field and/or near-fieldultrasonic sensors can be employed. Moreover, the location of each ofthe sensors 38,40 can vary. In some embodiments, for example, thefar-field ultrasonic sensor 38 is configured to transmit acoustic waves62 primarily in a forward direction from the distal tip 64 whereas thenear-field ultrasonic sensor 40 is configured to transmit side-orientedacoustic waves 66 from the side of the housing 48. Other configurationsare also possible.

FIG. 3 is a schematic view showing the distal section 52 of theultrasound imaging device 30 of FIG. 2 in greater detail. As can befurther seen in FIG. 3, and in some embodiments, an interior space 74within the housing 48 houses a rotating driveshaft 76 coupled to each ofthe ultrasonic sensors 38,40. The driveshaft 76 serves as mechanicallink from the drive and control system 28 to the ultrasonic sensors38,40. In some embodiments, the rotating driveshaft 76 may further serveas an electrical link for one or both of the ultrasonic sensors 38,40for conveying electrical signals back and forth between the sensors38,40 and signal processing circuitry of the controller 32.

During imaging, rotary motion 60 from the driveshaft 76 vis-a-vis thedrive and control system 28 is used to rotate each of the ultrasonicsensors 38,40 within the interior space 74. This rotary motion impartedto the ultrasonic sensors 38,40 serves to sweep the acoustic waves 62,66within the anatomical space surrounding the device 30, providing theoperator with a larger field of view and, in some cases, allowing theoperator to view adjacent objects without having to reposition thedevice 30 within the body. Rotary motion from the driveshaft 76 to thefar-field ultrasonic sensor 38, for example, causes the sensor 38 todirect the acoustic waves 62 360° in a field of view perpendicular to alongitudinal axis of the housing 48, allowing the operator to viewanatomical structures and other medical devices in the far-field. Rotarymotion from the driveshaft 76 to the near-field ultrasonic sensor 40, inturn, causes the sensor 40 to direct the acoustic waves 62 in aconical-shaped field of view in front of the device 30, allowing theoperator to determine various tissue characteristics of adjacent bodytissue in the near-field.

An acoustically transparent window or aperture 78 within the wall of thehousing 48 facilitates the transmission of acoustic waves 62 from thefar-field ultrasonic sensor 38 through the housing 48 and into thesurrounding anatomy. The distal tip 64 further serves as an acousticwindow or aperture to facilitate the transmission of acoustic waves 66from the near-field ultrasonic sensor 38 through the tip 64 and into thesurrounding anatomy. In some embodiments, an acoustic coupling fluidwithin the interior space 74 of the housing 48 serves to couple theacoustic energy transmitted and received via the ultrasonic sensors38,40 to the anatomy surrounding the device 30. In some cases, the fluid56 located within the interior space 74 of the housing 48 may also serveto cool the ultrasonic sensors 38,40 during use.

In some embodiments, the face 80 of the far-field ultrasonic sensor 38is oriented in a slightly forward direction at a transmission angle αrelative to a transverse line that is perpendicular to the longitudinalaxis L of the housing 48. In certain embodiments, for example, thesensor face 80 can be oriented at a transmission angle α of betweenabout 0 to 60 degrees, and more specifically about 10 to 40 degreesoff-axis. During imaging, the orientation of the sensor face 80 directsthe acoustic wave 62 in a slight forward direction, allowing theoperator to better view anatomy and objects that are located distally ofthe ultrasonic sensor 38. As further shown in FIG. 3, and in someembodiments, the face 82 of the near-field ultrasonic sensor 40 is alsooriented at a transmission angle β relative to the longitudinal axis ofthe housing 48. In certain embodiments, for example, the sensor face 82can be oriented at a transmission angle β of between about 0 to 60degrees, and more specifically, about 10 to 40 degrees off-axis. Duringimaging, this orientation of the sensor face 82 serves to increase theeffective field of view of the near-field ultrasonic sensor 40.

In the embodiment of FIG. 3, the angles α, β at which each of thesensors 38,40 are oriented within the housing 48 are fixed. In otherembodiments, however, the transmission angles α, β of the sensors 38,40can be made adjustable to permit the operator to alter the direction ofthe acoustic waves 62,66 relative to the device 30. In certainembodiments, for example, one or both of the ultrasonic sensors 38,40can be coupled to an independent servo motor that can be used toindependently adjust the angle of the sensor faces 80,82 during imaging.

The ultrasonic sensors 38,40 can comprise a single ultrasonic element ormultiple transducer elements. In those embodiments which employ multipletransducer elements, beam steering techniques may be used to alter thedirection of the acoustic waves 62,66 at specific angles relative to thedevice 30. In certain embodiments, for example, phase delays may beprovided on all or a subset of the transducer elements to focus theacoustic waves 62,66 towards a target imaging location, allowing theoperator to direct the acoustic energy on a desired anatomicalstructure, tissue sample, or other location within body for furtheranalysis. Other means for altering the direction, size, shape, as wellas other characteristics of the acoustic waves 62,66 can also beemployed. In some embodiments, for example, an acoustic lens may be usedto focus the acoustic energy towards a particular location within thebody.

FIG. 4 is a schematic view showing the distal section 86 of anultrasound imaging device 88 in accordance with another illustrativeembodiment. The device 88 is similar to the device 30 shown in FIG. 3,with like elements labeled in like fashion in the figures. In theembodiment of FIG. 4, however, each of the ultrasonic sensors 38, 40 arecoupled to a respective actuator 90,92 that rotates each of sensors38,40 within the interior space 74 of the housing 48. A first motor 90coupled to the far-field ultrasonic sensor 38, for example, isconfigured to independently rotate the ultrasonic sensor 38 360° in afield of view perpendicular to the longitudinal axis of the housing 48,allowing the operator to view anatomical structures and other medicaldevices adjacent to the device 30. A second motor 92, in turn, iscoupled to the near-field ultrasonic sensor 40, and is configured torotate the near-field ultrasonic sensor 40 within the distal tip 64 toview body tissue and other anatomy/objects in a forward-orienteddirection.

Although the device 88 in FIG. 4 utilizes multiple, discrete actuators90,92 to independently rotate each of the ultrasonic sensors 38,40, inother embodiments a single actuator (e.g., a motor) may be used torotate each of the ultrasonic sensors 38,40 simultaneously. Moreover,additional actuators may be employed to permit the independentadjustment of the transmission angle of each of the ultrasonic sensors38,40 in addition to the actuators 90,92 used for rotating the sensors38,40 within the housing 48.

FIG. 5 is a schematic view showing the distal section 94 of anultrasound imaging device 96 in accordance with another illustrativeembodiment. The device 96 is similar to the device 30 shown in FIG. 3,with like elements labeled in like fashion in the figures. In theembodiment of FIG. 5, however, the driveshaft 76 is coupled to only thefar-field ultrasonic sensor 38 and a separate actuator 98 is used toindependently rotate the near-field ultrasonic sensor 40. As with otherembodiments herein, additional actuators may be employed to adjust thetransmission angle of each of the ultrasonic sensors 38,40.

FIG. 6 is a schematic view showing the distal section 100 of anultrasound imaging device 102 in accordance with another illustrativeembodiment. The device 102 is similar to the device 30 shown in FIG. 3,with like elements labeled in like fashion in the figures. In theembodiment of FIG. 6, the device 102 further includes a steering wire104 that can be used to used to steer the distal tip 64 within the body,allowing the operator to further direct the acoustic energy towards aparticular location within the body. A similar steering wire can also beemployed in other embodiments described herein in order to permit theoperator to steer the distal tip within the body.

FIG. 7 is a flow diagram showing an illustrative process 106 forvisualizing anatomical structures, body tissue, and other medicaldevices within the body using the ultrasound imaging device 30 of FIG.2. FIG. 7 may represent, for example, several steps that can be usedduring a mapping and ablation procedure to visualize a mapping/ablationcatheter and the surrounding anatomy during an interventional cardiacelectrophysiology procedure.

The process 106 may begin generally at block 108, in which theultrasound imaging device 30 is inserted into the body and advancedintravascularly to an area of interest within the body. In certainelectrophysiology procedures, for example, the device 30 may be insertedinto the body via an artery or vein (e.g., the femoral artery) andadvanced through the body under fluoroscopic guidance to an area ofinterest such as the fossa ovalis of the right atrium. One or moreadditional devices may also be inserted into the body and advanced tothe area of interest (block 110). In a mapping and ablationelectrophysiology procedure, for example, a mapping/ablation cathetermay be inserted into the body and advanced to a location within the bodyunder fluoroscopic guidance for identifying and treating target ablationsites in or near the heart.

With the ultrasound imaging device 30 positioned at the area ofinterest, the operator may then activate one or both of the ultrasonicsensors 38,40 to visualize anatomical structures at the area of interestas well as the positioning of any other device(s) relative to thosestructures. The ultrasonic sensors 38,40 can be activated to produceimages of the environment surrounding the device 30, eithersimultaneously or at different times during the procedure. In someembodiments, for example, the far-field ultrasonic sensor 38 may beactivated to gather general information about the anatomy at the area ofinterest, and to determine the precise position of any other device ordevices located within the body using a tracking subsystem (block 112).Based on images obtained from the far-field sensor 38, the operator maythen select one or more further sites at the area for further analysisusing the near-field ultrasonic sensor 40 (block 114). If, for example,the operator detects a potential target ablation site within the heartusing a mapping/ablation catheter, the operator may advance theultrasound imaging device 30 to the target area to determine whether thetissue is healthy tissue, to determine whether an ablation lesion istransmural or continuous with adjacent lesions, or to determine othercharacteristics of the tissue. In some procedures, the images producedby the near-field ultrasonic sensor 40 can be used to confirm whetherthe mapping/catheter is in contact with the tissue to be treated. Insome embodiments, the images received from each of the ultrasonicsensors can be combined together with other images to obtain a compositeimage. For example, the ultrasonic images can be combined with imagesfrom a fluoroscope, CT-scan, MRI-scan, and/or other source to obtain acomposite image.

Based on the images generated by the ultrasound imaging device 30, theoperator may then perform the treatment on the patient. If, for example,an aberrant conductive pathway in the heart is identified using amapping/ablation catheter, the operator may then position the catheterat the site of the pathway under direct visualization with one or bothof the ultrasonic sensors 38,40 and perform ablation therapy on thepathway to treat the heart (block 116).

FIG. 8 is a view showing the ultrasound imaging device 30 of FIG. 2implanted in the right atrium 118 of the heart 120 and configured forvisualizing a medical probe 20 relative to surrounding cardiac anatomy.In the example procedure shown in FIG. 8, the ultrasound imaging device30 is shown inserted into the right atrium 118 (e.g., via the inferiorvena cava or abdominal aorta) and positioned at an area of interest nearthe fossa ovalis 122. A medical probe such as a mapping/ablationcatheter 20 is also shown inserted into the body and advanced to thearea of interest. The ultrasound imaging device 30 and mapping/ablationcatheter 20 can be positioned in the body, for example, by percutaneousintroduction through an introducer sheath inserted via an artery or vein(e.g., via a femoral artery and inferior vena cava) using fluoroscopy.

Once both devices 20,30 are positioned at the area of interest, and ascan be further seen in an enlarged view in FIG. 9, the far-field andnear-field ultrasonic sensors 38, 40 can be activated to generateacoustic waves 62, 66 within the surrounding anatomy. The ultrasonicsensors 38, 40 can be activated either simultaneously or at differenttimes, depending on the procedure. In the example procedure shown inFIG. 9, for example, both the far-field and near-field ultrasonicsensors are activated simultaneously, allowing the operator tosimultaneously visualize the mapping/ablation catheter 20 and fossaovalis 122 in the far-field using the far-field ultrasonic sensor 38,and cardiac tissue 124 located at the site of the fossa ovalis 122 inthe near-field using the near-field ultrasonic sensor 40. In otherembodiments, the process of visualizing anatomical structures andobjects in the far-field and body tissue in the near-field can beperformed at different times during the procedure.

If, during the procedure, the operator desires to further visualizeanatomy or objects within the body, the operator may readjust theposition of the ultrasonic imaging device 30 within the body. In certainembodiments, for example, the positioning can be changed by advancing orretracting the ultrasonic imaging device 30, and/or by manipulating asteering wire coupled to the distal section 52. In some embodiments, anactuator coupled to the ultrasonic sensor 38, 40 and/or beamsteeringtechniques can also be used to adjust the transmission angle of theacoustic waves 62, 66 transmitted by each of the ultrasound sensors 38,40.

As the mapping/ablation catheter 20 is moved around within the heartunder direct visualization from the ultrasound imaging device 30, themapping processor is operated to record electrical activity within theheart and derive mapping data. If an aberrant region is identified, thedistal tip 126 of the catheter 20 is placed into contact with thetargeted ablation region. In some procedures, the near-field ultrasonicsensor 40 can be advanced to a location adjacent to the site of thecatheter distal tip 126 to ensure that the tip 126 is engaged againstthe target tissue at the precise location identified via the mappingdata. An RF generator is then operated to begin ablating the tissue, andif instability in the catheter 20 is detected, additional images of thecatheter 20 and tissue adjacent to the catheter can be taken to ensurethat the catheter 20 is still properly positioned. If necessary, theoperator may then readjust the positioning of the catheter 20 until theablation is complete. The process can then be performed for anyadditional target tissue sites that are identified.

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of the presentinvention. For example, while the embodiments described above refer toparticular features, the scope of this invention also includesembodiments having different combinations of features and embodimentsthat do not include all of the described features. Accordingly, thescope of the present invention is intended to embrace all suchalternatives, modifications, and variations as fall within the scope ofthe claims, together with all equivalents thereof.

What is claimed is:
 1. An ultrasound imaging device adapted forinsertion within a body, comprising: an elongate housing having alongitudinal axis, a proximal section, a distal section, a firstacoustic window extending circumferentially about the housing, a secondacoustic window defining a distal tip of the housing, and an interiorspace within the housing extending from the proximal section to thedistal section; a first ultrasonic sensor including a plurality of firsttransducer elements configured to operate in alternating pulsing andsensing modes, the first ultrasonic sensor disposed within the distalsection of the housing and oriented to transmit substantiallyside-directed ultrasonic waves through the first acoustic window at afirst frequency for acquiring far-field images within the body; and asecond ultrasonic sensor disposed on the longitudinal axis configured tooperate in alternating pulsing and sensing modes, the second ultrasonicsensor disposed within the distal tip of the housing and oriented totransmit forward-directed ultrasonic waves through the second acousticwindow at a second frequency greater than the first frequency foracquiring near-field images within the body.
 2. The ultrasound imagingdevice of claim 1, wherein the device is configured to provide phasedelays on all or a subset of the first transducer elements to focusacoustic waves generated thereby towards a target imaging location. 3.The ultrasound imaging device of claim 1, wherein at least one of thefirst and second ultrasonic sensors is rotatable about the longitudinalaxis relative to the housing.
 4. The ultrasound imaging device of claim3, further comprising a rotating driveshaft coupled to the firstultrasonic sensor.
 5. The ultrasound imaging device of claim 1, whereinthe first ultrasonic sensor is configured to direct ultrasonic waves ata transmission angle of between about 10 to 40 degrees relative to thelongitudinal axis.
 6. The ultrasound imaging device of claim 1, whereinthe second ultrasound sensor is configured to direct ultrasonic waves ata transmission angle of between about 10 to 40 degrees relative to thelongitudinal axis.
 7. The ultrasound imaging device of claim 1, furthercomprising at least one electrode configured for sensing electricalactivity within the body.
 8. An ultrasound imaging device adapted forinsertion within a body, comprising: an elongate housing having alongitudinal axis, a proximal section, a distal section, a firstacoustic window extending circumferentially about the housing, a secondacoustic window defining a distal tip of the housing, and an interiorspace within the housing extending from the proximal section to thedistal section; a first ultrasonic sensor configured to operate inalternating pulsing and sensing modes, the first ultrasonic sensordisposed within the distal section of the housing and oriented totransmit substantially side-directed ultrasonic waves through the firstacoustic window at a first frequency for acquiring far-field imageswithin the body; and a second ultrasonic sensor disposed on thelongitudinal axis, the second ultrasonic sensor including a plurality oftransducer elements configured to operate in alternating pulsing andsensing modes, the second ultrasonic sensor disposed within the distaltip of the housing and oriented to transmit forward-directed ultrasonicwaves through the second acoustic window at a second frequency greaterthan the first frequency for acquiring near-field images within the body9. The ultrasound imaging device of claim 8, wherein the device isconfigured to provide phase delays on all or a subset of the transducerelements of the second ultrasonic sensor to focus acoustic wavesgenerated thereby towards a target imaging location.
 10. The ultrasoundimaging device of claim 8, wherein at least one of the first and secondultrasonic sensors is rotatable about the longitudinal axis relative tothe housing.
 11. The ultrasound imaging device of claim 10, furthercomprising a rotating driveshaft coupled to the first ultrasonic sensor.12. The ultrasound imaging device of claim 8, wherein the firstultrasonic sensor is configured to direct ultrasonic waves at atransmission angle of between about 10 to 40 degrees relative to thelongitudinal axis.
 13. The ultrasound imaging device of claim 8, whereinthe second ultrasound sensor is configured to direct ultrasonic waves ata transmission angle of between about 10 to 40 degrees relative to thelongitudinal axis.
 14. The ultrasound imaging device of claim 8, furthercomprising at least one electrode configured for sensing electricalactivity within the body.
 15. An ultrasound imaging device adapted forinsertion within a body, comprising: an elongate housing having alongitudinal axis, a proximal section, a distal section, a firstacoustic window extending circumferentially about the housing, a secondacoustic window defining a distal tip of the housing, and an interiorspace within the housing extending from the proximal section to thedistal section; a first ultrasonic sensor including, the firstultrasonic sensor disposed within the distal section of the housing andconfigured to transmit substantially side-directed ultrasonic wavesthrough the first acoustic window at a first frequency for acquiringfar-field images within the body; and a second ultrasonic sensordisposed on the longitudinal axis within the distal tip of the housingand oriented to transmit forward-directed ultrasonic waves through thesecond acoustic window at a second frequency greater than the firstfrequency for acquiring near-field images within the body, wherein atleast one of the first and second ultrasonic sensors includes aplurality of transducer elements configured to operate in alternatingpulsing and sensing modes.
 16. The ultrasound imaging device of claim15, wherein the device is configured to provide phase delays on all or asubset of the transducer elements to focus acoustic waves generatedthereby towards a target imaging location.
 17. The ultrasound imagingdevice of claim 15, wherein at least one of the first and secondultrasonic sensors is rotatable relative to the housing about thelongitudinal axis.
 18. The ultrasound imaging device of claim 17,further comprising a rotating driveshaft coupled to the first ultrasonicsensor.
 19. The ultrasound imaging device of claim 15, wherein the firstultrasonic sensor is configured to direct ultrasonic waves at atransmission angle of between about 10 to 40 degrees relative to thelongitudinal axis, and wherein the second ultrasound sensor isconfigured to direct ultrasonic waves at a transmission angle of betweenabout 10 to 40 degrees relative to the longitudinal axis.
 20. Theultrasound imaging device of claim 15, further comprising at least oneelectrode configured for sensing electrical activity within the body.